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Tips to Prevent and Treat Phytophthora in CA Citrus

February 15, 2019
This agronomic image shows a citrus tree.

Phytophthora continues to be a damaging pathogen in CA citrus groves. It attacks root systems, trunks, fruit and ultimately, entire trees. Tree health decline can occur rapidly within a year, especially under wet conditions.

There are 2 main types of Phytophthora that effect citrus:

  1. Phytophthora gummosis: Damage symptoms include sap oozing from small cracks in the infected bark creating a bleeding appearance. Eventually, the bark dries, cracks and falls off. Lesions eventually spread around the trunk, and leaves yellow and drop.
  2. Phytophthora root rot: Damage symptoms include leaves that yellow and drop, root bark that slides off easily when pinched, and destroyed feeder roots.

Here are 4 tips to optimize citrus tree health in both types of Phytophthora:

  1. Manage water usage. Do not allow water to stand around the crowns of trees or to hit the tree trunk regularly. Provide drainage in low spots of the orchard, areas that are prone to flooding and where water penetration is poor throughout the season.
  2. Protect the bark of the tree. Whenever a tree’s bark is harmed or cut, it leaves an opening for the Phytophthora pathogen to enter. Be careful when mowing your grove.
  3. Evaluate soil samples. If you are unsure about any of these symptoms, consider taking a soil sample for parasitica or P. citrophthora. Syngenta offers the Soil Pathogen Assessment (SPA), a free program that assesses Phytophthora infections. Contact your Syngenta representative to learn more about soil sampling through the SPA program.
  4. Prepare with a fungicide application. Ridomil Gold® SL fungicide can protect against root rot and increase feeder root growth to ensure better water and nutrient use efficiency through the entire tree.

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